Effect of axial conduction on the heat transfer in micro-channels

Experimental and numerical analysis were performed to evaluate heat transfer characteristics of water flowing through triangular silicon micro-channels with hydraulic diameter of 160 mum in the range of Reynolds number Re = 3.2-64. It was shown that as the bulk water temperature, as well as the temperature of the heated wall, do not change linearly along the channel. The experimental results of temperature distribution on the heated wall agree with the numerical predictions. The behaviour of the Nusselt number along the channel has a singular point. At this point, the difference between the temperatures on the wall and the bulk water becomes negative and the flux changes the sign and is directed from the fluid to the wall. The singular point shifts closer to the channel outlet with an increase of the Reynolds number. It was shown that under conditions of the present study the heat transfer may be described by conventional Navier-Stokes and energy equations as a common basis. (C) 2004 Elsevier Ltd. All rights reserved.